rate for the remaining valves. Where an unexpected result
is observed it is a simple matter of elimination to identify
the valve that causes this, enabling the commissioning
engineer to ‘home in’ on the problem area.”
Lowe adds: “It is only a short stretch of the imagination to a
situation where remote control valves are used in conjunction
with electronic flow measurement, allowing all of this to be
done from a PC. It would then only become necessary to
enter the ceiling void if problems are encountered.”
One important issue that arises is the impact this
approach has on witnessing procedures, as CIBSE Code
W was written before the advent of pressure-independent
valves and the increased use of variable volume systems.
“Code W’s tolerances of -0,+10 l/s for actual flow rates,
compared with design flow rates, aren’t really necessary or,
“With conventional proportional balancing, the indeed, suitable for variable volume systems using pressure-
commissioning engineer needs to balance the entire
system before problem circuits can be identified. Once
The scope
independent valves,” Lowe says. “With pressure-independent
valves it’s no longer necessary to focus on the accuracy and
those problems have been resolved the whole system then of the remote tolerance to achieve design flow because of the ability of
needs to be balanced again, leading to a lengthy process that
commissioning
the system to provide higher flows. The focus should be
can impact on the whole construction schedule.
“The SSB method is different because it uses a subtraction
concept provides
redirected to the environmental condition being provided
at the most economic and energy efficient savings.”
technique to identify problem valves. This is based on considerable food There’s no doubt that the scope of the remote
knowing the design flow rates for each individual valve and,
for thought
commissioning concept provides considerable food for
therefore, the total flow rate for that group of terminal units. thought. And, if Lowe’s ideas are widely adopted, they could
Assuming all the valves are functioning correctly, isolating impact on the overall cost of construction as well as making
each valve will have a predictable effect on the total flow hydronic systems more competitive with VRF. l
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www.cibsejournal.com February 2009 CIBSE Journal 69
CIBSEfeb09pp66-69 chilledV2•.indd 69 5/2/09 14:39:56
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